title: A randomized study on the effect of vitamin D₃ supplementation on skeletal muscle morphology and vitamin D receptor concentration in older women.
abstract: BACKGROUND
  Studies examining whether vitamin D supplementation increases muscle mass or muscle-specific vitamin D receptor (VDR) concentration are lacking.
  
  
  OBJECTIVE
  Our objective was to determine whether vitamin D₃ 4000 IU/d alters muscle fiber cross-sectional area (FCSA) and intramyonuclear VDR concentration over 4 months.
  
  
  METHODS
  This was a randomized, double-blind, placebo-controlled study in a single center.
  
  
  METHODS
  Participants were 21 mobility-limited women (aged ≥ 65 years) with serum 25-hydroxyvitamin D (25OHD) levels of 22.5 to 60 nmol/L.
  
  
  METHODS
  Baseline and 4-month FCSA and intramyonuclear VDR were measured from vastus lateralis muscle cross-sections probed for muscle fiber type (I/IIa/IIx) and VDR using immunofluorescence.
  
  
  RESULTS
  At baseline, mean (±SD) age was 78 ± 5 years; body mass index was 27 ± 5 kg/m², 25OHD was 46.3 ± 9.5 nmol/L, and a short physical performance battery score was 7.95 ± 1.57 out of 12. At 4 months, 25OHD level was 52.5 ± 17.1 (placebo) vs 80.0 ± 11.5 nmol/L (vitamin D [VD]; P < .01), and change in 25OHD level was strongly associated with percent change in intramyonuclear VDR concentration-independent of group (r = 0.87, P < .001). By treatment group, percent change in intramyonuclear VDR concentration was 7.8% ± 18.2% (placebo) vs 29.7% ± 11.7% (VD; P = .03) with a more pronounced group difference in type II vs I fibers. Percent change in total (type I/II) FCSA was -7.4% ± 18.9% (placebo) vs 10.6% ± 20.0% (VD; P = .048).
  
  
  CONCLUSIONS
  Vitamin D₃ supplementation increased intramyonuclear VDR concentration by 30% and increased muscle fiber size by 10% in older, mobility-limited, vitamin D-insufficient women. Further work is needed to determine whether the observed effect of vitamin D on fiber size is mediated by the VDR and to identify which signaling pathways are involved.
authors.affiliation: MD, MS, Division of Endocrinology, Diabetes, and Metabolism, Tufts Medical Center, 800 Washington Street, Box 268, Boston, MA 02111. lisa.ceglia@tufts.edu.
authors.forename: Lisa
authors.initials: L
authors.lastname: Ceglia
authors.forename: Sathit
authors.initials: S
authors.lastname: Niramitmahapanya
authors.forename: Mauricio
authors.initials: M
authors.lastname: da Silva Morais
authors.forename: Donato A
authors.initials: DA
authors.lastname: Rivas
authors.forename: Susan S
authors.initials: SS
authors.lastname: Harris
authors.forename: Heike
authors.initials: H
authors.lastname: Bischoff-Ferrari
authors.forename: Roger A
authors.initials: RA
authors.lastname: Fielding
authors.forename: Bess
authors.initials: B
authors.lastname: Dawson-Hughes
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D019412:Anatomy, Cross-Sectional; D002112:Calcifediol / Q000097:blood; D002762:Cholecalciferol / Q000378:metabolism / Q000627:therapeutic use*; D015331:Cohort Studies; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D015577:Geriatric Assessment; D006801:Humans; D051346:Mobility Limitation; D024510:Muscle Development; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism / Q000473:pathology; D018657:Muscle Fibers, Slow-Twitch / Q000378:metabolism / Q000473:pathology; D053580:Muscle Strength; D010865:Pilot Projects; D052097:Quadriceps Muscle / Q000378:metabolism / Q000473:pathology*; D018167:Receptors, Calcitriol / Q000819:agonists / Q000378:metabolism*; D015854:Up-Regulation; D014808:Vitamin D Deficiency / Q000097:blood / Q000178:diet therapy* / Q000378:metabolism / Q000473:pathology
chemical_list: D018167:Receptors, Calcitriol; C579457:VDR protein, human; D002762:Cholecalciferol; D002112:Calcifediol